Polyhedral oligomeric silsesquioxane-conjugated bis(diphenylphosphino)amine ligand for chromium(III) catalyzed ethylene trimerization and tetramerization

Polyhedral oligomeric silsesquioxanes (POSSs) were attached to conventional bis(diphenylphosphino)amine (PNP) ligand as solubility-enhancing materials for catalytic ethylene trimerization and tetramerization. Differently functionalized arylphosphine ligands of the type (Ph)2PN(POSS)P(Ph)(ArR) (R = functional groups) were systematically developed, and their corresponding chromium(III) complexes were formed. The developed precatalysts exhibited excellent tolerance in solvents, including even low-carbon-number hydrocarbons such as n-pentane, n-hexane, or cyclohexane. In particular, the ortho-fluorophenyl-substituted complex showed higher stability even at higher temperatures above 120 °C. The ortho-OCF3–phenyl-substituted complex showed outstanding catalytic activity, which reached 2287 kg/g Cr/h at 30 bar.